Assuming that by space the asker means outer space or the vacuum of space, there are a few problems with this question.

First, it's impossible to know how loud the sun would be if space weren't a vacuum. This is because the sound pressure of a star depends on its surface temperature, and we have no way of measuring the surface temperature of the sun.

Second, even if we could measure the surface temperature of the sun, it's not clear how that would help us answer the question. Sound travels through air (or any other gas) by compressing and expanding the gas molecules around it. But there is no air in space, so there is no way for sound to travel